Treatment of hydrocarbon oils



NOV- 14, 4 NELSON TREATMENT OF HYDROCARBON OILS Filed Jan. 6, 1952 CON NSER 30 FRACTIONATOR\ INVENTOR EDWIN F. NELSON BY; Z

ATTOR Y Patented Nov. 14, 1933 UNITED STATES.

TREATMENT OF HYDROCARBON OILS Edwin F. Nelson, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota Application January 6, 1932. Serial No. 585,010

Claims.

: ucts.

The primary purpose of the present invention is to provide an improved method and means of decreasing or substantially preventing the formation and/or accumulation of coke or carbonaceous material in the reaction chamber of a cracking system. The primary principles of the invention comprise increasing the velocity of flow of residual liquid from the inlet to the outlet of the reaction zone of a cracking system, thereby decreasing the time during which said residual liquid is subjected to conversion and preventing its conversion to the point wherein substantial quantities of coke or carbonaceous materials are formed. Q

In the type of cracking operation wherein hydrocarbon oil is subjected to conversion conditions in a heating element, the heated material is discharged into the upper portion of a reaction chamber, from the lower portion of which both vaporous conversion products and residual liquid are withdrawn to a zone of reduced pressure, difliculties are sometimes encountered, due to the formation of coke or carbonaceous material in the reaction chamber. The purpose of an operation of this type is to subject materials which remain in a vaporous state in the reaction v zone to continued conversion therein while liquid products are quickly separated from the vapors and withdrawn from the reaction zone without substantial further conversion, the theory being that quick separation is effected by the difierence in weight between the liquid and vaporous materials, causing the liquid to gravitate more rapidly than the vapors to the bottom of the chamber. It is common practice in this type of operation to spray the material entering the reaction chamber from the heating element against the walls of the chamber, thus permitting the liquid products to flow in a thin film down the walls of the chamber. When there is a sufiicientquantity of residual liquid, little or no difficulty from coking is encountered in this type of operation, however, in some cases, particularly when operating with relatively light oils as charging stock, there is not a suflicient quantity of residual oil formed to maintain a positive and rapid flow of liquid down the walls of the reaction chamber, consequently the relatively small quantity of residual liquid formed is subjected to a prolonged time in the reaction zone, resulting in its excessive conversion and formation of substantial quantities of coke or carbonaceous material. The use of the features of the present invention are particularly advantageous in this type of cracking operation and as adapted to this type of system may comprise restricting the surface over which the residual liquid must flow during its passage to the outlet from the reaction zone, thus increasing the amount of oil per unit area of its path of flow and thereby increasing the velocity of the stream of residual oil. The invention is, however, not limited to use in this or any other specific type of cracking system but is limited only to increasing the velocity of-liquid conversion products during their passage through a conversion zone by de creasing the surface area over which they must pass.

Many specific forms of apparatus may be utilized in accomplishing the process of the present invention and it is not intended to limit the invention to any specific form of apparatus, all forms which accomplish the same or similar results being within the spirit and scope of the invention.

The attached diagrammatic drawing illustrates a form of cracking apparatus such as previously described to which the principles of the present invention have been applied. The following description of the drawing includes a description of -the process of the present invention as it may be practiced in the apparatus illustrated.

Figure 1 of the attached drawing is a side elevation of the entire cracking system.

Figure 2 -is an enlarged sectional plan view of the reaction chamber taken along a plane indicated by the line 2-2 in Figure 1.

Figure 3- is a sectional elevation of a similar reaction chamber showing a modification of the means illustrated in Figures 1 and 2 for increasing the velocity of the residual liquid flowing through the reaction chamber. The entire drawing is diagrammatic and is not intended to represent the true proportions of the apparatus.

Referring now to Figs. 1 and 2: The raw oil charging stock to be treated may be supplied through line 1 and valve 2 to pump 3 from which it is fed through line 4,,valve 5 and line 6 to heating element '7. Any well known means of preheating the raw oil may be employed, if desired, prior to' its introduction into heating element 7 although not illustrated in the drawmeans of heat supplied from a furnace 8 of any suitable form. The heated oil is discharged from heating element 7 through line 9 and valve 10 to reaction chamber 11. Reaction chamber 11 is also preferably maintained at a substantial super-atmospheric pressure and in the specific form of apparatus here illustrated, the heated materials from heating element 7 may enter the upper portion of chamber 11 being directed by means of an extension 9 of transfer line 9 against the inner surface of the walls of chamber 11 at a point such as indicated at 12 in Figure 2. In order to restrict the surface over which the residual oil may flow in its downward path through chamber 11, projections or bailies 13 may be attached to the walls of the chamber by welding or any other suitable means. In this manner instead of permitting the residual oil to spread over the entire inner surface of the walls of chamber 11 it may be restricted to any desired portion of the wall, thus decreasing the surface over which the oil flows, increasing the volume of oil per unit area of its path of flow, thereby increasing the velocity of the stream of residual oil flowing through the chamber and decreasing its time of exposure to the conversion conditions maintained in the reaction chamber. Vaporous materials including both that portion of the heated oil from heating element '7 introduced into chamber 11 in a vaporous state and vapors evolved from the residual oil during its passage through this zone flow downward through the chamber at a slower rate than the residual oil and are thereby subjected to the conversion conditions in chamber 11 for a greater length of time than the residual oil.

Both liquid and vaporous products are withdrawn from chamber 11 through line 14, and valve 15 to reduced pressure vaporizing chamber 16 wherein, by virtue of the reduced pressure employed in this zone relative to that in chamber 11, the conversion products are cooled and further vaporization of the residual oil is effected. Residual liquid remaining unvaporized in chamber 16 may be withdrawn to cooling and storage or to any other further treatment through line 17 and valve 18. Vapors from chamber 16 are withdrawn through line 19 and valve 20 to fractionation in fractionator 21.

The relatively heavy components of the vapors supplied to fractionator 21 are condensed by fractionation in this zone, collecting in the lower portion thereof to be withdrawn through line 22 and valve 23 to pump 24 from which they are returned through line 6 and valve 25 to heating element 7 for further conversion, together with the raw oil charging stock supplied to this zone, as already described. A part of the vapors may be removed from the top of chamber 11 to prevent formation of a dead space therein and passed through line 26, controlled by valve 2'7, to the *fractionator. v

Vapors are withdrawn from the upper portion of fractionator 21 through line 28 and valve 29 to be subjected to condensation and cooling in condenser 30. Distillate and uncondensable gas passes from condenser 30 through line 31 and valve 32 to be collected in receiver 33. Uncondensable gas may be released from the receiver through line 34 and valve 35. Distillate may be withdrawn from the receiver through line 36 and valve 3'7. If desired, a portion of the distillate from receiver 33 may be recirculated, by well known means not illustrated in the drawing, to

the upper portion of fractionator 21 to assist cooling and fractionation in this zone.

Referring now to Figure 3'which, as already mentioned, illustrates another means of increasing the velocity of residual liquid flowing through the reaction chamber and thereby decreasing its time in this zone: the reaction chamber which is similar to chamber 11 is designated as 11. As in Figure 1, line 9 connects the reaction chamber with the heating element and the extension 9" of line 9 inside chamber 11 directs the heated material onto a cylindrical shaft 38 extending from near the top of the chamber to near the bottom of the chamber and supported in any well known manner, not illustrated in the drawing. The residual liquid may flow downward over the outer surface of shaft 38, passing from its lower end to the discharge line 14 through which both the residual oil and the vaporous conversion products, which latter pass downward through the chamber at a slower rate than the residual oil, are withdrawn to the vaporizing zone of the system.

The process of the present invention may employ conversion temperatures ranging, for example, from 800 to 1200 F., more or less, and pressures ranging from substantial atmospheric to super-atmospheric pressures as high as 2000 pounds or more per eq. in. The particular cracking system above illustrated and described preferably employs substantial super-atmospheric pressures of the order of to 500 pounds or more per sq. in. in both the heating element and re--, action chamber. Substantially equalized or differential pressure may be employed between these two zones. The preferred range of conversion temperatures at the outlet from the heating element are from 850 to 950 F., more or less. A substantial reduced pressure of the order of 100 pounds or thereabouts per sq. in. down to substantially atmospheric pressure is preferably employed in the vaporizing chamber, which pressure may be substantially equalized or reduced in the fractionating, condensing and collecting portions of the system.

As a specific example of the operation of the process ofthe present invention, a 42 A. P. I. gravity Pennsylvania distillate is the charging stock supplied to the system. A temperature of about 920 F. is maintained at the outlet from the heating element and a substantially equalized pressure of approximately 400 pounds per sq. in. is maintained in both the heating element and reaction chamber. The heated material from the heating element is directed against a portion of the inner wall of the reaction chamber and the path of flow of the residual liquid -is confined to a channel down the wall of the raction chamber, having a width approximately one-twentieth of the circumference of the chamber. The vaporizing, fractionating, condensing and collecting portions of the system are maintained under a substantially/equalized pressure of approximately 50 pounds per sq. in. This operation may result in the production of about 75 percent of motor fuel of high antiknock value, about 8 percent of heavy residual oil and about 600 cubic feet of gas per barrel of charging stock, substantially no appreciable amount of coke or carbonaceous material is formed in the reaction chamber and the residual oil is substantially free of suspended coke or carbonaceous material. To illustrate the advantages of thisoperation over a. similar operation utilizing the same charging stock and the same conversion conditions with the exception that the material from the heating element is allowed to flow over substantially the entire inner surface of the reaction chamber, the yield and characteristics of the motor fuel produced may be substantially the same as in the operation above outlined but the operating cycle is less than half as long, due to the formation of carbonaceous material and plugging of the line between the reaction chamber and the vaporizing chamber. The residual oil produced by this latter operation may contain some 5 to 10 percent or thereabtus of suspended pitch-like and carbonactous material and an appreciable amount of coke is found in the reaction chamber.

I claim as my invention: a

1. In processes for cracking hydrocarbon oils of the character in which the oil is heated to a cracking temperature in an elongated heating coil, thence delivered to the upper portion of a vertically elongated reaction chamber from the lower end of which liquid and vapors are removed at such rate that no substantial accumulation of a liquid therein occurs, thence passed to a low pressure distillation zone where vaporization of unvaporized oil occurs by the contained heat thereof, the improvement which comprises liberating vapors from the heated oil in the upper portion of the chamber, confining the downward 2. In processes for cracking hydrocarbon oils of the character in which the oil is heated to a cracking temperature in an elongated heating coil, thence delivered to the upper portion of a vertically elongated reaction chamber from the lower end of which liquid and vapors are removed at such rate that no substantial accumulation of a liquid therein occurs, thence passed to a low pressure distillation zone where vaporization of unvaporized oil occurs by the contained heat thereof, the improvement which comprises liberating vapors-from the heated oil in the upper portion of the chamber, confining the downward flow of liquid oil through the vertically elongated chamber to an area not substantially exceeding one-tenth of the internal circumferential area of said chamber, and passing the vapors downwardly through substantially'the entire interior portion of the chamber and at a lower rate than the liquid oil. 7

3. In processes for cracking hydrocarbon oils of the character in which the oil is heated to a cracking temperature in an elongated heatingcoil, thence delivered to the upper portion of a vertically elongated reaction chamber from the lower end of which liquid and vapors are removed at such rate that no substantial accumulation of a liquid therein occurs, thence passed to a low pressure distillation zone where vaporization of unvaporized oil occurs by the contained heat thereof, the improvement which comprises liberating vapors from the heated oil in the upper portion of the chamber, accelerating the rate of flow of the liquid oil downwardly through the chamber by restricting the area in the chamber over which the liquid oil descends, and passing the vapors downwardly through substantially the entire interior portion of the chamber and at a lower rate than the liquid oil.

4. The improvement-as defined in claim 3 further characterized in that the flow of liquid oil downwardly through the chamber takes place along and is restricted to a limited portion of the wall of the chamber.

5. The improvement as defined by claim 3 further characterized in that the flow of liquid oil downwardly through the chamber is confined to the central portion of the chamber.

EDWIN F. unison. 

